The invention relates to a method of removing hydrogen sulfide (H.sub.2 S) from a fluid stream whereby the stream is treated with an aqueous solution of ferric chelates to remove substantially all of the hydrogen sulfide gas contained therein and the solution also contains an anionic polymer whereby the chelating agent is stabilized against degradation.
It is well known in the prior art that iron chelates are useful to remove H.sub.2 S from sour gas streams. See for example U.S. Pat. No. 4,622,212, Columns 1 and 2. It also has been proposed that various organic compounds can be added as stabilizers for the iron chelates. This is illustrated by the following U.S. Pat. Nos. 4,382,918; 4,388,293; 4,400,368; 4,421,733; and 4,461,754.
Sonoda (U.S. Pat. No. 4,002,727) discloses an aqueous solution composition for removing hydrogen sulfide from a gas stream, in which the aqueous solution comprises iron in concentrations of 1-5000 ppm, possibly in the form of iron-EDTA. Additionally, the aqueous solution of Sonoda et al. comprises 0.1-10 g/1 of a water-soluble anionic polymer such as polymethacrylic acid (column 5, line 5), and the sodium salts thereof. The Sonoda process requires the use of a water soluble derivative of anthraquinone or naphthoquinone such as naphthoquinone sulfonate and anthraquinone disulfonic acid. The present process is quite different from the Sonoda process because the present invention does not occur in the presence of a water soluble derivative of anthraquinone or naphthoquinone such as naphthoquinone sulfonate and anthraquinone disulfonic acid.